Octane Boosters

[GaryNo]

In my area we have good availability of ethanol-free gasoline. The few stations that have premium (93 octane) are disappearing. There seems to be a trend to carry only mid-grade (90 octane). The Rotax manual for the 912 ULS states that minimum of 91 octane fuel should be used. There are octane boosters, from auto parts stores, that can be added to the fuel to raise the octane by as much as 3 numbers. Anyone have any comments, knowledge, or info on this topic? Thanks Gary :)

[avidflyer]

I tested some non oxygenated premium fuel with some justice brothers octane buster in it in a tall skinny plastic bottle that I used for checking for alcohol in the fuel. I put some fairly new cut off pieces of fiberglass in the bottle also as I wanted to see if the fuel would hurt the fiberglass. Didn't seem to hurt the fiberglass at all, but it melted the plastic bottle so it started leaking. I had used it lots of times with regular non ox. fuel many times before and it never hurt the bottle then. Never used that stuff again. Jim Chuk

[Av8r3400]

Personally, I'd be very, very leery of using automotive octane boosters.

Why not just mix in a couple gallons per tank of 100LL?

[Paul Z]

I mix 100 LL with with 88 MoGas and have had no problems.

[GaryNo]

Thanks for your input. I like the idea of mixing 100LL to the mogas. Simple and compatible. Gary :)

[hansedj]

We have been using HiTest octane Booster for 3 years now with no problems. We get it at our Do it best hardware store. Thought about mixing but didn't want the lead. On long trips we have use 100ll adding Decalin

[Av8r3400]

I wouldn't touch that stuff with a ten foot pole… MSDS (http://www.rockymountainatvmc.com/docs/MSDS_Maxima%20Hi-Test%20Octane%20Booster.pdf)

It is Toluene and Alcohol. Probably okay with the newer tanks, but it will destroy the old ones.

IMO - Much safer with a splash of 100LL to bring the mo-gas octane up a point or two. That small amount of lead won't be a factor in the motor.

[SkySteve]

AV8r3400,
As a point of reference, how much 100 LL do you add to non-ethanal, say 88 octane mogas?

[Av8r3400]

I'm very lucky in that I can still get un contaminated fuel here in Wisconsin.

From my point of view, I'd say if you were trying to get 88 to 91 by adding 100, I'd estimate at least a 2/3 to 1/3 mix of mo to avgas. Maybe a 50:50 mix just to be safe?

As the previous poster was asking, from 90 to 91, I'd say a couple gallons to each tank would more than suffice.


(Just using simple weighted average computation)

[Paul Z]

I believe it would be a simple average calculation. I am not a Chemical Engineer, but it sound logical. According to my calculation if you have a 13 Gallon wing tank. It should take approximately 3.5 Gallons per 13 Gallons to result in 91.23 Octaine. Ahh, I just posted and I see AV8R3400 came up with the Average as well. I was surprised it would only take 3 Gallons to get you that close to 91 Octaine.

[neville]

For my 912iS I mix 4 gal 92 mogas with 1 gal 100LL. The local Rotax shop
recommended this with the comment that Rotax engines like a little 100LL.
The mix is well below the operators manual point for requiring Decalin and more frequent oil changes.

[Paul Z]

For my 912iS I mix 4 gal 92 mogas with 1 gal 100LL. The local Rotax shop
recommended this with the comment that Rotax engines like a little 100LL.
The mix is well below the operators manual point for requiring Decalin and more frequent oil changes.

That should be 90.4 octane, I like the idea of changing oil less than every 25 hours.

[Av8r_Sed]

I worked the bulk of my career for a refining technology company. I've worked on online octane analyzers and on a team dedicated to octane analysis for refinery blending operations. I can assure you that octane number cannot be predicted accurately as a linear function of two components.

The good news is that the ratios being discussed of 88 unleaded to 100LL will most likely result in a higher octane boost than the average calculations would indicate. Anyone following this advise should be good to go. They just won't know their exact octane number.